It is a problem in the field of printing systems to print wear resistant MICR characters on a document. Magnetic ink character recognition (MICR) printing apparatus make use of a magnetically sensible toner to imprint machine readable indicia on documents. The toner is applied to the document in a standard electrophotographic printing process to generate the MICR characters on the document.
The MICR characters typically are fused to the surface of the documents by the use of a pair of rollers. The fusing roller is heated internally by a halogen lamp while the pressure roller has a silicone rubber surface. By "wringing" the paper between these two rollers, the toner is bonded or fused to the paper. Alternatively, a "cold" fusing system can be used which chemically melts the toner on the paper. In this system, the printed MICR characters do not go through pressure rollers. The fused MICR characters therefore stand higher on the document and are more susceptible to wear.
It is a problem in existing MICR printer apparatus systems that the magnetic read heads cause smearing of the MICR characters when the document has been read in magnetic readers a number of times. The character smearing causes errors in the machine reading of the MICR characters and necessitates manual intervention to read the MICR characters on the document.
Typical documents using printed MICR characters are negotiable checks, billions of which are processed daily. Each check has a line of MICR characters printed on the bottom of the check to identify the originator, home bank, amount of the check, etc. The check is returned to its home bank once it is cashed by processing it through the Federal Reserve System clearinghouses. There the check is read by passing it through a magnetic reader that deciphers the data contained in the line of MICR characters. Each check is read at least four times by a magnetic reader and sometimes over twenty times before returning to its home bank. The magnetic reading process is abrasive and can be destructive to the line of printed MICR characters, causing read errors.
One existing solution to this problem is illustrated in the Troy.RTM. 308 Financial Document Printer that treats each finished document with a coating that prevents the MICR toner from smearing. The coating is applied all over the entire document to provide a lubricating agent on the surface of the document to minimize smearing of the printed and fused MICR characters. A problem with such an arrangement is that the coating used in this printer is an expensive lubricant in the form of a powder and brushing it on the entire document causes the use of far more lubricant than is required to protect the MICR characters. Lubricating the entire document surface also renders future writing or printing on the document surface difficult.